Field of the Art
Described is an integrated circuit that has power control functionality and, in particular, power path selection based upon various input settings.
Background
As modern portable systems become more flexible and sophisticated, there has become a need to be able to utilize all of the available options that can be used to keep the mobile device either charged or powered up. These charging options can be from things such as a wall charger (the most common) or a wireless charging system or a USB compatible input port. But more recently there has emerged a further need for powering certain sections of the mobile device by using near field communications (NFC). In these applications the power for the receiving mobile device may be derived from the proximity to the NFC transmitting device. In all of these applications there is a need to be able switch between different power input sources to be able to provide power to the mobile device.
Power multiplexers have been used in other applications such as switching between a normal VCC voltage and a high voltage (HV) input in order to either read or write from a programmable logic device or an EEPROM device. However most of these applications require the user to select from one input or the other by way of a separate select pin. Recently, products have been introduced that will select one of two inputs as long as one of the inputs is above the UVLO (under voltage lockout) threshold and the other is not. If both inputs exceed the UVLO threshold, then the user must again use a separate select input pin to tell the device which input has priority to be connected to the output.